Chainring Teeth
10-10-10 | 04:29 PM
#1
Thread Starter
Plutonium Member
Joined: Jul 2010
Posts: 39
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Chainring Teeth
I just noticed some broken teeth on my FSA 36/46T chainring (see below). What causes this? My bike is only 4 months old with 700 miles on it. The chain is not skipping and the drivetrain seems to operate fine. I can't seem to find a direct replacement for the 46T FSA chainring. Any suggestions?
10-10-10 | 04:47 PM
#2
Senior Member
Joined: Jul 2005
Posts: 11,754
Likes: 26
From: Mesa, AZ
Bikes: Moots RCS, tandem, beach-cruiser, MTB, Specialized-Allez road-bike, custom track-bike
It's a pre-cut shape to improve shifting:
1. the steel pin picks up the chain on the inside
2. the flat-top cut-down tooth is lower than the others and helps the chain wrap up and over the chainring
3. the two teeth behind it encountres the chain at an angle. The cut-out chamfer matches the angle of the chain and helps it slide down over the teeth
Shimano started this with their SG chainrings about 15-years ago. Basically the chainrings are "pre-worn" in the areas where shifting occurs.
1. the steel pin picks up the chain on the inside
2. the flat-top cut-down tooth is lower than the others and helps the chain wrap up and over the chainring
3. the two teeth behind it encountres the chain at an angle. The cut-out chamfer matches the angle of the chain and helps it slide down over the teeth
Shimano started this with their SG chainrings about 15-years ago. Basically the chainrings are "pre-worn" in the areas where shifting occurs.
10-10-10 | 04:51 PM
#3
Senior Member
Joined: Apr 2009
Posts: 39,897
Likes: 3,865
From: New Rochelle, NY
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
+1, these are shifting gates and are the "glide" in hyperglide. This might be the number one question asked by new bike purchasers ever since shifting gates were introduced.
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FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
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